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AS8.3 | Pharmacologic Management of Pain — SDL Guide (Part 3)
Self-Assessment: Applying Analgesic Pharmacology to Clinical Scenarios
The following self-assessment prompts help you verify mastery of the pharmacological principles required by NMC 2024 competency AS8.3 before proceeding to clinical application.
Consider the following scenarios and reason through the analgesic selection:
Scenario A: A 40-year-old woman with fibromyalgia — widespread musculoskeletal pain, sleep disruption, and fatigue with no identifiable structural lesion — is asking for 'something stronger' after codeine provided minimal relief. What is the pharmacological basis for her poor opioid response? What first-line pharmacological and non-pharmacological interventions are supported by evidence?
Scenario B: A 65-year-old man on warfarin for atrial fibrillation requires analgesia following a dental extraction. He has moderate renal impairment (eGFR 35 mL/min) and a history of peptic ulcer. Which analgesics can be safely prescribed? What dose of paracetamol is appropriate?
Scenario C: A 55-year-old woman with diabetic peripheral neuropathy scores her neuropathic foot pain at 6/10 NRS, poorly controlled on paracetamol alone. You prescribe amitriptyline 10 mg nocte. She asks: 'How does this antidepressant help my pain — I'm not depressed?' Provide a patient-appropriate explanation based on the pharmacological mechanism covered in this module.
Scenario D: An opioid-naïve 70-year-old man is started on modified-release morphine 10 mg twice daily for chronic back pain. What four immediate co-prescriptions are mandatory to anticipate adverse effects, and what monitoring is required for respiratory depression risk?
Reflecting on these scenarios, notice the common thread: pharmacological mechanism first, then drug selection — never the reverse. Knowing that fibromyalgia is a central sensitisation syndrome explains why opioids are largely ineffective; knowing that amitriptyline enhances descending noradrenergic inhibition explains its analgesic efficacy at sub-antidepressant doses; knowing that M6G accumulates in renal failure predicts the safer alternatives to morphine in that context. Mechanism-based prescribing is the hallmark of competent analgesic pharmacology.
CLINICAL PEARL
The laxative is not optional. Every patient started on a regular opioid — regardless of the opioid, route, or dose — must receive a stimulant laxative co-prescription from day one. Opioid-induced constipation is the one major opioid adverse effect that does not undergo tolerance; patients on long-term opioids who are not prescribed a laxative will develop severe constipation, faecal impaction, and autonomic complications. Senna 2–4 tablets at night, or bisacodyl 5–10 mg at night, is appropriate as the starting regimen. For patients in whom oral laxatives fail despite adequate doses, consider methylnaltrexone SC (a peripherally restricted μ antagonist that does not reverse analgesia). Documenting the laxative prescription alongside the opioid is a marker of safe prescribing practice.